Barlow, 42, who has collaborated with the singer for his new solo album 'Since I Saw You Last', said the star could not resist showing off pictures of the boys when they were in the recording studio together, reported Contactmusic.
"We had a few hours in the studio recording this track for the record, but it was so sweet to see him reach in his bag and pull out his ipad and start showing us all pictures of the kids and he was so proud.
The 'Rocket Man' hitmaker and husband David Furnish have sons Zachary, two, and Elijah, 10 months.